Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$58.33	3.786%	$60.5384	$60.54	$60.55	$60.50
Purchase #2	$113.39	3.661%	$117.5412	$117.54	$117.55	$117.50
Purchase #3	$48.68	5.560%	$51.3866	$51.39	$51.40	$51.40
Purchase #4	$49.30	4.616%	$51.5757	$51.58	$51.60	$51.60
Purchase #5	$125.33	11.348%	$139.5524	$139.55	$139.55	$139.60
Purchase #6	$198.67	8.732%	$216.0179	$216.02	$216.00	$216.00
Purchase #7	$90.27	11.781%	$100.9047	$100.90	$100.90	$100.90
7 purchase totals =	$683.97		$737.5169	$737.52	$737.55	$737.50